ASTART.E. MOLLUSCA. LUCINAD^E. 441 



6. A. lineata Obovate, transversely depressed ; slightly truncated ; with 



a few concentric acute ridges, and many minute intervening striae upon the 

 surface ; lunette lanceolate, small ; margin entire — Sower. Min. Conch. 

 t. clxxix. f. 1. — Upper Oolite. 



7. A. excavata Obovate, convex, concentrically costated, truncated re- 



trallv ; lunette hemispherical, excavated ; cartilage enclosed in a sulcus ; 

 margin toothed.— -Sower. Min. Conch, t. ccxxxiii — Under Oolite. 



8. A. planata Transversely obovate, gibbose, with small obtuse concentric 



ridges ; edges crenulated ; lunette concave — Sower. Min. Conch, t. cclvii. — 

 In Crag. 



9. A. rugata Obovate, anteriorly subtruncated, when young transversely 



costated, afterwards slightly wrinkled ; edge internally crenulated ; lunette 

 concave, obovate, pointed — Soiver. Min. Conch, t. cccxi — London Clay. 



10. A. ohovata Obovate, uniformly convex, corrugated ; lunette com- 

 pressed ; anterior margin subtruncated, inner edge crenulated. — Sower. Min. 

 Conch, t. cccliii. — Iron Sand. 



11. A. frigonalis. — Cordato-triangular, depressed, transversely sulcated ; 

 beak pointed ; anterior side separated by an angle, smooth — Sower. Min. 

 Conch, t. ccccxliv. f. 1. — Inferior Oolite. 



12. A. orbicularis. — Lenticular, witli many concentric reflected lamellte up- 

 on its surface ; edge smooth. — Sower. Min. Conch, t. ccccxliv. f. 2, 3. — Upper 

 Oolite. 



13. A. ptimila. — Obliquely obovate, slightly convex, with numerous con- 

 centric ridges ; edge crenated within — Soiver. Min. Conch, t. cccxliv. ;f. 4. 

 5, 6. — Upper Oolite, 



14. A. striata — Lenticular, transversely striated ; lunette ovate, flat, deep- 

 ly sunk, shell thick — Sower. Min. Conch, t. dxx. f. 1 Ch-een Sand. 



15. A. m-bicularis. — Lenticular, rather gibbose, concentrically furrowed ; 

 furrows small ; posterior surface plaited with an angle at its edge, lunette 

 elongated, very deep. — Soiver. Min. Conch, t, dxx. f. 2. — Oolite. 



16. A. imlricata. — Cordate, orbicular, largely imbricated, convex ; tooth in 

 the left valve beneath the lunette small ; lunette elongated, flat ; hinge line 



arched; edge finely crenulated. — Sower. Min. Conch, t. Dxxi. f 1 Suffolk, 



Crag. 



17- A. nitida — Transversely obovate, angular above, rather depressed, mi- 

 nutely sulcated near the beaks, the rest even ; beaks pointed ; lunette lan- 

 ceolate ; edge crenated — Sower. Min. Conch, t. Dxxi. f. 2.— Suffolk, Crag. 



18. A. bipartita — Obcordate, gibbose ; six or eight large undulations upon 

 a flat space near the beak, the rest of the surface even ; beaks acute ; edo-e 

 toothed. — Sower. Min. Conch, t. Dxxi. f. 3. — Suffolk, Crag. 



19. A. oblonga — Transversely oblong, convex ; surface largely waved ; 

 beaks small ; lunette cordate, pointed, concave ; edge crenated.~-Sower. Min. 

 Conch, t. Dxxi. f. 4 — Suffolk, Crag. 



Gen. CXXIV. LUCINA. — Orbicular, two teeth in each valve, 

 with lateral teeth. 



* StricB concentric. 



504. L. rcuhila. — Shell with numerous raised striae, and shal- 

 low, broadp intervening spaces. 



